POLYMER SHRINKS AND SWELLS

Abstract

THE OSCILLATING Belousov-Zhabotinsky (BZ) reaction, famous for producing dazzling color-changing patterns, is now also finding use as a novel way to move matter. Shingo Maeda of Waseda University, in Tokyo, and colleagues designed a polymer gel that undulates with a peristaltic motion similar to the way cilia or intestinal muscles pulse with rhythmical, directional contractions. As the gel undergoes the BZ reaction, a ruthenium catalyst periodically changes its oxidation state back and forth, generating chemical waves that propagate outward, causing the gel to shrink and swell ( Angew. Chem. Int. Ed. 2008, 47 , 6690). The authors write that they envision use of the phenomenon to develop lifelike systems—“biomimetic devices such as autonomous matter transporters or self-beating micropumps that could function without external control.” The new gel, composed of a cross-linked polymer and ruthenium, is activated by dunking it in a solution of citric acid, which sets off the BZ reaction. Eventually, the reacti...